April Dutta

Title: April Dutta: Innovator in Photolithography and Charged Particle Inspection Systems

Introduction

April Dutta is a prominent inventor based in Milpitas, CA (US). She has made significant contributions to the fields of photolithography and charged particle inspection systems. With a total of 3 patents, her work has advanced the technology used in microcircuit fabrication.

Latest Patents

One of her latest patents is titled "Fast image simulation for photolithography." This innovative method simulates photolithography using conventional image processing techniques. The process involves convolution to simulate blurring, while erosion and dilation correct for edge diffraction. In this technique, the source image of the photomask is deconvolved to sharpen it and then dilated to remove edge diffraction. The image is subsequently eroded and convolved according to the resolution of the stepper at the photomask plane. This aerial image can be further eroded to match the effects of resist and developing. Optional thresholding is performed to produce a simulated processed wafer image. In a faster technique, the deconvolution step is eliminated, and dilation and erosion are combined into a single erosion. When a phase shift mask is involved, a complex convolution is utilized. Source data can originate from the photomask electronic design or from a visual image of the actual photomask. Optimizations include special microprocessor instructions, floating point pixel values, separable convolution, and annular illumination simulation.

Another significant patent is the "Electron beam inspection system and method." This invention encompasses a method and apparatus for a charged particle scanning system and an automatic inspection system, which includes wafers and masks used in microcircuit fabrication. A charged particle beam is directed at the surface of a substrate for scanning, and a selection of detectors is included to detect secondary charged particles, back-scattered charged particles, and transmitted charged particles from the substrate. The substrate is mounted on an x-y stage to provide at least one degree of freedom while being scanned by the charged particle beam. Additionally, the substrate is subjected to an electric field on its surface to accelerate the secondary charged particles. The system facilitates inspection at low beam energies on charge-sensitive insulating substrates and accurately measures the position of the substrate concerning the charged particle beam. An optical alignment system is also included for initially aligning the substrate beneath the charged particle beam. To function efficiently, a vacuum system is employed for evacuating and